The present invention is related generally to the field of orthodontics. More particularly, the present invention is related to improved systems and methods for removably attaching a dental positioning appliance to the dental features of a patient during orthodontic treatment.
Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning teeth is accomplished by applying controlled forces to the teeth over an extended period of time. This is conventionally accomplished by wearing what are commonly referred to as xe2x80x9cbraces.xe2x80x9d Braces comprise a variety of appliances such as brackets, bands, archwires, ligatures, and O-rings. The brackets and bands are bonded to the patient""s teeth using a suitable material, such as dental adhesive. Once the adhesive has set, the archwire is attached to the brackets by way of slots in the brackets. The archwire links the brackets together and exerts forces on them to move the teeth over time. Twisted wires or elastomeric O-rings are commonly used to reinforce attachment of the archwire to the brackets. Attachment of the archwire to the brackets is known in the art of orthodontia as xe2x80x9cligationxe2x80x9d and wires used in this procedure are called xe2x80x9cligatures.xe2x80x9d The elastomeric O-rings are called xe2x80x9cplastics.xe2x80x9d
After the archwire is in place, periodic meetings with the orthodontist are required, during which the patient""s braces will be adjusted. This involves installing different archwires having different force-inducing properties or by replacing or tightening existing ligatures. Between meetings, the patient may be required to wear supplementary appliances, such as elastic bands or headgear, to supply additional or extraoral forces.
Although conventional braces are effective, they are often a tedious and time consuming process requiring many visits to the orthodontists office. Moreover, from a patient""s perspective, they are unsightly and uncomfortable. Moreover, the archwire and ligatures which connect the brackets in a continuous network make brushing, flossing between the teeth and other dental hygiene procedures difficult, possibly contributing to the development of gingivitis. Consequently, alternative orthodontic treatments are needed. In particular, it would be desirable to use appliances which can be removed by the patient during daily dental hygiene routines, while participating in athletic activities, or for cosmetic purposes.
A particularly promising approach relies on the use of elastic positioning appliances for realigning teeth. Such appliances comprise a thin shell of elastic material that generally conforms to a patient""s teeth but is slightly out of alignment with the initial tooth configuration. Placement of the elastic positioner over the teeth applies controlled forces in specific locations to gradually move the teeth into the new configuration. Repetition of this process with successive appliances comprising new configurations eventually move the teeth through a series of intermediate configurations to a final desired configuration. A full description of an exemplary elastic polymeric positioning appliance is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present invention. Both documents are incorporated by reference for all purposes.
In addition to their ease of use, polymeric positioning appliances are generally transparent, providing an improved cosmetic appearance, and impart substantial force on the teeth, due to stiffness of the appliance. The stiffness of an elastic positioning appliance is a result of the modulus of the thermoformable polymer materials from which it is made. The higher the modulus of the materials, the higher the stiffness of the appliance. When a patient positions such an appliance over a prescribed group of teeth, one or more of the teeth will provide a base or anchor region for holding the positioning appliance in place while the stiffness of the polymeric material will impart a resilient repositioning force against one or a portion of the remaining teeth. By designing the appliance to cover the teeth, a much larger contact surface area is afforded compared to traditional spring retainers and wire-based appliances. However, such anchoring and repositioning abilities of removable elastic positioning appliances are still dependent on the physical features and configuration of the patient""s teeth, palette, and previous dental work, to name a few. For example, shell-like elastic polymeric positioning appliances have difficulty applying certain forces to individual teeth, such as extrusive force (e.g., pulling or raising a tooth relative to the jaw).
Thus, it would be desirable to provide tooth positioners, systems, and methods which apply adequate force in desired directions to selected teeth at specific times during treatment. In particular, it would be desirable to enable the fabrication and use of removable positioners and systems which can apply extrusive, rotational, and other directional forces which have heretofore been difficult to apply with removable positioners. It would also be desirable to reduce the cost of the orthodontic treatment and retain the patient benefits of a removable appliance in cases where they might not otherwise be available. At least some of these objectives will be met by the designs and methods of the present invention described hereinafter.
The present invention provides improved devices, systems and methods for removably attaching a dental positioning appliance to the dental features of a patient during orthodontic treatment. Such removable dental positioning appliances usually comprise an elastic polymeric shell having a cavity for receiving at least some of a patient""s teeth and are often preferred over conventional braces for tooth repositioning due to comfort, appearance and ease of use. These appliances function by applying force to specific surfaces of the teeth or dental features to cause directed movement. However, the type of movement and level of force applied is usually dependent on the surface characteristics and positions of the dental features. In many cases, the native tooth surface(s) and other dental features of a patient are inadequate to provide sufficient anchoring or to impart sufficient force on the teeth to be repositioned. To overcome these limitations, the present invention uses one or more attachment devices which may be attached to preselected attachment points on the teeth or dental features to provide the appropriate physical leverage. Specific design and location of these attachment devices may provide newly achievable and/or more effective repositioning forces, anchoring ability and appliance retention. The systems and methods of the present invention provide the design, production and use of such attachment devices with removable dental positioning appliances in orthodontic treatment.
The use of attachment devices in combination with removable dental positioning appliances provides the patient with the benefits of removable appliances while retaining the ability to extrude, rotate, and otherwise manipulate teeth as with conventional braces. Like conventional braces, attachment devices may be bonded to the surface of the teeth in order to provide physical features which facilitate the application of controlled force. The attachment devices of the present invention may have a very simple construction, in some instances being only a bump, bead, wedge, or other body or structure which can be fixedly attached to the surface of a tooth or other dental feature in order to transmit force generated by the dental positioning appliance to the dental feature and/or to anchor the positioning appliance to teeth in order to permit the appliance to apply forces elsewhere in the patient""s teeth. In such instances, the attachment device acts simply as a handle or lever to assist in the transmission of force between the teeth and the dental positioning appliance. In other instances, the attachment device may feature a hook, similar in design to those used for mounting elastic bands. The hook may be engaged with a number of ligatures, bands, filaments, coils or other connecting members to effect repositioning of the teeth, usually in combination with the dental positioning appliance. The hook may serve as an anchor in the repositioning of other teeth, or it may serve as a point of purchase to apply directed force to the surface of the tooth to which it is bonded.
The attachment devices of the present invention, unlike conventional braces, are typically small, infrequent, (i.e., present on very few of the patient""s teeth) unnoticeable to others, and do not interfere with dental hygiene practices. Usually, the attachment device will have a small base e.g., up to 4 mm across (mesial-distal) and up to 6 mm long (gingiva-crown). An attachment device body may typically protrude up to a maximum of 2.5 mm. This is significantly smaller than standard brackets or bands used in convention braces which may protrude up to 4 mm. The devices may be bonded in specific locations throughout the dentition where appropriate and this may only be required at one or a few locations. Thus, the infrequency of the device, in addition to the size, also reduces its visibility and awareness to the patient. Likewise, the attachment device may be bonded to any surface of the teeth, including lingual surfaces which would allow the devices to be largely unnoticeable to others. In these cases, shape and design considerations would prevent any irritation to the contacting tissues, such as the tongue, inner lip and inner cheek. When placed in visible areas, the attachment device may be color matched to the dental surface to further diminish its visibility. In addition, such attachment devices are typically designed to removably attach to a removable dental appliance. Thus, when the appliance is removed, routine brushing, flossing and dental care may be undertaken in the usual manner.
Brackets used with conventional braces, such as those used to support elastic bands or headgear, are limited in design and therefore application of use. Generally, these attachment devices have a large profile, protruding 2-4 mm, which is not conducive to use with elastic positioning appliances or other devices designed to be removably positioned over the attachment device. Likewise, their surface geometry is limited to a few prescribed functions which are specific to use with conventional braces. Thus, they are not adequately capable of providing functions necessary to the present invention, such as removably attaching a dental positioning appliance.
In a first aspect of the present invention, the attachment devices are comprised of an attachment body having a base. The base may simply be the portion of the attachment body which will be bonded to the surface of the dental feature. Alternatively, the base may be an enlarged portion of the body, designed to increase the surface area of the bond. Likewise, the base may be removable or permanently attached. The attachment body may feature a variety of designs, most commonly being bumps, beads, wedges, also including but not limited to hooks, clasps, bands, brackets, buttons, snaps, springs, levers, rods, tubes, coils, indents and/or other protrusions. Each design may serve one or a number of purposes in repositioning of the teeth. For example, a clasp may be used to attach a portion of a removable positioning appliance to the attachment device. This attachment device design may be desired for anchoring of the appliance or applying force to the dental feature to which the attachment device is bonded. Additional devices may be used in conjunction with the attachment body to attach the appliance to the attachment device. For example, adhesives, flexible bands or connecting ligatures may be used in conjunction with the design of the attachment body to aid in connection to the appliance. In one such case, an attachment body located on the lower jaw may be attached to a removable appliance placed on the upper jaw by means of a flexible band. This may afford desired force vectors that are unobtainable by other means. Alternatively, the attachment body may be comprised of specific design features to aid in properly seating a removable elastic repositioning appliance, in addition to anchoring the appliance in place to apply repositioning forces. A preferred embodiment of these design features includes an attachment body with a sloping face e.g., a wedge.
The phrase xe2x80x9cdental featurexe2x80x9d will apply to any portion of the patient""s teeth which may be contacted by a dental positioning appliance and/or engaged by an attachment device. Usually, the dental feature will be a portion of a surface of a natural tooth, but in some instances could be a portion or a surface of an artificial tooth, e.g., a dental implant, or a non-natural surface or repair of a native tooth, e.g., a filling, crown, inlay, restoration, or the like. Thus, the phrase dental feature will generally refer to all natural and non-natural teeth in a patient""s dentition. In a second aspect of the present invention, the attachment device is bonded to and/or formed over a dental feature in a desired location. The attachment device may be bonded to any of these features with any suitable bonding material, typically dental restorative composites. The location in which one or more of these attachment devices are bonded is dependent upon the desired repositioning goal. The devices may be bonded to any surface of the dental features and may be placed singly or in groups. Likewise, a given attachment device may be bonded to surfaces of more than one dental feature. In a preferred embodiment, an attachment device may placed on each of two teeth located on opposite sides of one or a contiguous group of teeth. When an elastic positioning appliance is inserted and attached to the two attachment devices, an intrusive force may be applied to the tooth or teeth in between. This is counterintuitive to the methods of conventional orthodontics in which brackets are bonded to the teeth that require repositioning.
In a third aspect of the present invention, the attachment devices may be constructed from variety of materials, including but not limited to metals, glass or silicone filled polymers, and other composite materials. Such materials are typically designed to be chip, break and shear resistant for durability. The base of the attachment device may be constructed from the same or from different materials as the attachment body. Likewise, the attachment body may be permanently or removably mounted on the base or the body and base may be constructed as one entity.
In a preferred embodiment, the attachment device may be constructed from a polymer material or combination of materials which have been formulated to be sensitive to an environmental condition or external stimulus. Upon exposure to such a condition or stimulus, the material may undergo a predetermined state change, which may be temporary or permanent. For example, upon exposure, a rigid material may become temporarily malleable, allowing changes in geometry to be made. Upon removal of the condition or stimulus, the material may return to its original rigid state and geometry or it may return to its original rigid state with the new geometry. In the former case, such stimulus may be used to facilitate coupling an attachment device to an elastic positioning appliance. The stimulus may alter the geometry of the attachment device during insertion and placement of the appliance. Removal of the stimulus may allow the device to return to its original geometry for application of repositioning forces. A full description is provided in application Ser. No. 09/250,262, the full disclosure of which is incorporated herein by reference. In the latter case, such stimulus may be used to facilitate bonding of the attachment device to the surface of the dental feature. The stimulus may alter the state and geometry of the attachment device, or simply the base, to conform it to the surface of the dental feature to which it is to be bonded. Upon removal of the stimulus, the attachment device may remain in the new geometry, providing a larger contacting surface area for bonding.
Similarly, a malleable material may be molded into a desired form and polymerized by exposure to an environmental condition or stimulus. Such polymerization may permanently hold the material in the desired form. This may be useful in both constructing the attachment device and bonding the device to a dental surface. For example, malleable material may be inserted in a mold of an attachment device. Polymerization, as described above, may result in a rigid attachment device in the molded form. In a preferred embodiment, the mold of the attachment device may be an impression in the wall of an elastic positioning appliance. This may ensure proper surface geometry for association between the attachment device and the appliance. Likewise, polymerization of the material while the appliance is in place over the dental features may simultaneously bond the attachment device to the dental feature. This may ensure proper alignment of the attachment device and the receiving impression in the appliance, and it may also preclude the need for additional bonding materials.
In a fourth aspect of the present invention, methods are provided to produce and/or bond an attachment device to a dental feature. Three preferred embodiments are applicable for use with elastic repositioning appliances or similarly fabricated devices and are as follows: 1) basic casting, 2) casting with polymerizing material and 3) computer-aided casting with polymerizing material. An example of basic casting involves producing two identical attachment devices by any means and comprised of any material(s). One attachment device may be placed in a desired location on a dental surface of the patient. The other attachment device may be placed in the identical location on a mold replicating at least the dental surface. An elastic positioning appliance or similar device may be formed over the mold containing the attachment device. Upon removal, a negative impression of the attachment device may be seen in the wall of the elastic positioning appliance. Therefore, when the appliance is inserted and seated in position by the patient, the impression in the appliance will correspond with the attachment device bonded to the dental surface. If the attachment device is to be used as a point of purchase to effect movement of the dental feature to which it is attached, the attachment device may be bonded to the dental feature in a position or orientation that differs from the mold. Therefore, when the appliance is inserted by the patient, the impression in the appliance will be slightly out of alignment with the attachment device. This will apply force to the attachment device, resulting in gradual repositioning of the device and underlying dental feature.
The method of casting with polymerizing material is similar to basic casting. Like basic casting, an attachment device of any design and material is placed in a desired location on a mold replicating at least the dental surface of interest. Again, an elastic positioning appliance or similarly fabricated device may be formed over the mold containing the attachment device, creating a negative impression of the attachment device in the wall of the appliance. At this point, a malleable polymerizing material may be placed into the negative impression in the appliance. When the appliance is inserted and seated in position in the oral cavity, the polymerizing material will be in contact with the dental surface and will be in the proper position. The material may be polymerized by any means, typically by an external stimulus or environmental condition. Polymerization may simultaneously harden the material and bond the material to the dental surface. Upon removal of the appliance, the formed attachment device may remain in place on the dental surface.
The method of computer-aided casting with polymerizing material is similar to the methods described above, yet differs in the steps of creating the appliance. Here, a 3-D computerized image of the attachment device is virtually placed in a desired location on an image of the dental surface. A mold is produced from the images using any computer-guided model fabrication system, such as stereolithography, CNC machining, and laser machining. The result is a mold of at least the dental surface of interest with a replica of the attachment device in proper position. At this point, an elastic positioning appliance or similarly fabricated device may be formed over the mold containing the attachment device, creating a negative impression of the attachment device in the wall of the appliance. Again, a malleable polymerizing material may be placed into the negative impression in the appliance. When the appliance is inserted and seated in position in the oral cavity, the material may be polymerized, leaving a formed attachment device in place on the dental surface when the appliance is removed.
In a fifth aspect of the present invention, an additional method is provided to produce and/or bond an attachment device to a dental feature. Two preferred embodiments are applicable for use with any dental appliances. The first embodiment involves a multi-tooth template which may be used to produce and/or bond an attachment device to a dental feature. The multi-tooth template may be thin and flexible to fit over multiple dental features at once, allowing multiple attachment devices to be placed at the same time. Receptacles may be present in the template to receive a polymerizing material. When the template is inserted and seated in position in the oral cavity, the polymerizing material will be in contact with the dental surface and will be in the proper position. The material may be polymerized by any means, typically by an external stimulus or environmental condition. Polymerization may simultaneously harden the material and bond the material to the dental surface. Upon removal of the template, the formed attachment device may remain in place on the dental surface. This method may be similar or identical to casting with polymerizing material and computer-aided casting with polymerizing material, however it may differ in that the template may not be used as the repositioning appliance. This difference may afford the use of template designs that are not applicable to repositioning appliances. For example, the template may be comprised of a material that is unsuitable for a repositioning appliance, or it may contain additional design features, such as handles, that would interfere with such usage. Similarly, the template may be fabricated from a mold of the patient""s present tooth configuration, rather than the tooth configuration prescribed by an elastic positioning appliance. This may facilitate the method of attachment device production and/or bonding due to the closer fit of the template to the tooth configuration.
The second embodiment involves a single-tooth template which may be used to produce and/or bond an attachment device to a dental feature. The single-tooth template may be more rigid and may fit over a single dental feature. The template may be comprised of one or more receptacles to receive polymerizing material. When applied to the target surface of the dental feature, the material may be polymerized by any means previously described. The resulting attachment device is properly shaped and bonded in place. Alternatively, the single-tooth template may be comprised of a receptacle that is rigid, to receive the polymerizing material, surrounded by a thin, film-like portion of material that conforms to the dental feature. The thin, flexible area may contain an adhesive with which to hold the template in place on the dental feature. The material may then be polymerized to form the attachment device. When the procedure is complete, the template may be peeled off and discarded.
Single-tooth and multi-tooth templates may allow the production and placement of one or more attachment devices to a dental feature independent of the geometry of certain adjacent dental features. Thus, a template may be used throughout various stages of orthodontic repositioning treatment. This may be useful to replace an attachment device which has broken off mid-treatment or to place new attachment devices throughout treatment. As described above, at least one receptacle may be present in the template to receive a polymerizing material. When the template is inserted and seated in position in the oral cavity, the polymerizing material will be in contact with the dental surface and will be in the proper position. The material may be polymerized by any means, typically by an external stimulus or environmental condition. Polymerization may simultaneously harden the material and bond the material to the dental surface. Upon removal of the template, the formed attachment device may remain in place on the dental surface. Alternatively, templates may be used to bond any attachment device to a dental feature surface. For example, a pre-fabricated attachment device may be bonded to a surface with the use of a template. An attachment device may be inserted in a receptacle of a template, adhesive applied to the base of the attachment device and the template applied to the dental surface. After bonding has occurred, the template may be removed. Thus, the template may provide proper positioning and orientation. Likewise, a template may be used to form an attachment device using a polymerizing material, and then used again to bond the attachment device to a dental surface.
In a sixth aspect of the present invention, a method is provided to improve the production of templates or elastic positioning appliances. In a preferred embodiment, additional structures are provided in the mold of the dental feature with desired attachment device. The structures may be of any geometry and are typically placed near the gingival surface. When a template or appliance is thermoformed over the mold and additional structures, the structures provide a protrusion which aids in drawing the template or appliance from the mold. The protrusion may then be removed before use.
In a further aspect of the present invention, a method is provided to further improve the production of templates or elastic positioning appliances. In some cases, it may be desired to alter a template or appliance after it has been removed from a mold. Such alterations may include trimming edges or removing portions to prevent interference with specific devices or dental features. For example, it may be desirable to produce an elastic appliance with a window in a particular location corresponding to the placement of an attachment device. To ensure proper location of the window, a structure may be provided in the mold at the same location to aid in the creation of the window. In a preferred embodiment, a structure of spherical geometry may be provided in the mold at the desired location. Thermoforming of the appliance may result in a spherical protrusion at the location of the structure. After removal of the appliance from the mold, the spherical protrusion may be removed by cutting, filing, sawing, or any other means of removal. Thus, a window with a shape corresponding to the cross section of the structure, in this case a circle, may remain. As a result, a template or positioning appliance may be produced to cover desired dental features or to provide windows to expose such features.